In his own words...

Some years ago we developed a monospaced 12 pitch sans serif for a client. We also created a 10 pitch version that was later discarded. PropTen is the 10 pitch version modified to proportional widths. The name PropTen refers to ‘Proportional 10 Pitch’ which is a technical impossibility. It does have a slight ‘its time to vote’ twist to it. You know, ‘after you pick your candidate you also need to vote yes or no on the following Propositions, don’t forget Prop10, the team needs those uniforms.’